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-rw-r--r--qemu/include/block/aio.h444
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diff --git a/qemu/include/block/aio.h b/qemu/include/block/aio.h
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-/*
- * QEMU aio implementation
- *
- * Copyright IBM, Corp. 2008
- *
- * Authors:
- * Anthony Liguori <aliguori@us.ibm.com>
- *
- * This work is licensed under the terms of the GNU GPL, version 2. See
- * the COPYING file in the top-level directory.
- *
- */
-
-#ifndef QEMU_AIO_H
-#define QEMU_AIO_H
-
-#include "qemu-common.h"
-#include "qemu/queue.h"
-#include "qemu/event_notifier.h"
-#include "qemu/thread.h"
-#include "qemu/rfifolock.h"
-#include "qemu/timer.h"
-
-typedef struct BlockAIOCB BlockAIOCB;
-typedef void BlockCompletionFunc(void *opaque, int ret);
-
-typedef struct AIOCBInfo {
- void (*cancel_async)(BlockAIOCB *acb);
- AioContext *(*get_aio_context)(BlockAIOCB *acb);
- size_t aiocb_size;
-} AIOCBInfo;
-
-struct BlockAIOCB {
- const AIOCBInfo *aiocb_info;
- BlockDriverState *bs;
- BlockCompletionFunc *cb;
- void *opaque;
- int refcnt;
-};
-
-void *qemu_aio_get(const AIOCBInfo *aiocb_info, BlockDriverState *bs,
- BlockCompletionFunc *cb, void *opaque);
-void qemu_aio_unref(void *p);
-void qemu_aio_ref(void *p);
-
-typedef struct AioHandler AioHandler;
-typedef void QEMUBHFunc(void *opaque);
-typedef void IOHandler(void *opaque);
-
-struct AioContext {
- GSource source;
-
- /* Protects all fields from multi-threaded access */
- RFifoLock lock;
-
- /* The list of registered AIO handlers */
- QLIST_HEAD(, AioHandler) aio_handlers;
-
- /* This is a simple lock used to protect the aio_handlers list.
- * Specifically, it's used to ensure that no callbacks are removed while
- * we're walking and dispatching callbacks.
- */
- int walking_handlers;
-
- /* Used to avoid unnecessary event_notifier_set calls in aio_notify;
- * accessed with atomic primitives. If this field is 0, everything
- * (file descriptors, bottom halves, timers) will be re-evaluated
- * before the next blocking poll(), thus the event_notifier_set call
- * can be skipped. If it is non-zero, you may need to wake up a
- * concurrent aio_poll or the glib main event loop, making
- * event_notifier_set necessary.
- *
- * Bit 0 is reserved for GSource usage of the AioContext, and is 1
- * between a call to aio_ctx_check and the next call to aio_ctx_dispatch.
- * Bits 1-31 simply count the number of active calls to aio_poll
- * that are in the prepare or poll phase.
- *
- * The GSource and aio_poll must use a different mechanism because
- * there is no certainty that a call to GSource's prepare callback
- * (via g_main_context_prepare) is indeed followed by check and
- * dispatch. It's not clear whether this would be a bug, but let's
- * play safe and allow it---it will just cause extra calls to
- * event_notifier_set until the next call to dispatch.
- *
- * Instead, the aio_poll calls include both the prepare and the
- * dispatch phase, hence a simple counter is enough for them.
- */
- uint32_t notify_me;
-
- /* lock to protect between bh's adders and deleter */
- QemuMutex bh_lock;
-
- /* Anchor of the list of Bottom Halves belonging to the context */
- struct QEMUBH *first_bh;
-
- /* A simple lock used to protect the first_bh list, and ensure that
- * no callbacks are removed while we're walking and dispatching callbacks.
- */
- int walking_bh;
-
- /* Used by aio_notify.
- *
- * "notified" is used to avoid expensive event_notifier_test_and_clear
- * calls. When it is clear, the EventNotifier is clear, or one thread
- * is going to clear "notified" before processing more events. False
- * positives are possible, i.e. "notified" could be set even though the
- * EventNotifier is clear.
- *
- * Note that event_notifier_set *cannot* be optimized the same way. For
- * more information on the problem that would result, see "#ifdef BUG2"
- * in the docs/aio_notify_accept.promela formal model.
- */
- bool notified;
- EventNotifier notifier;
-
- /* Scheduling this BH forces the event loop it iterate */
- QEMUBH *notify_dummy_bh;
-
- /* Thread pool for performing work and receiving completion callbacks */
- struct ThreadPool *thread_pool;
-
- /* TimerLists for calling timers - one per clock type */
- QEMUTimerListGroup tlg;
-
- int external_disable_cnt;
-
- /* epoll(7) state used when built with CONFIG_EPOLL */
- int epollfd;
- bool epoll_enabled;
- bool epoll_available;
-};
-
-/**
- * aio_context_new: Allocate a new AioContext.
- *
- * AioContext provide a mini event-loop that can be waited on synchronously.
- * They also provide bottom halves, a service to execute a piece of code
- * as soon as possible.
- */
-AioContext *aio_context_new(Error **errp);
-
-/**
- * aio_context_ref:
- * @ctx: The AioContext to operate on.
- *
- * Add a reference to an AioContext.
- */
-void aio_context_ref(AioContext *ctx);
-
-/**
- * aio_context_unref:
- * @ctx: The AioContext to operate on.
- *
- * Drop a reference to an AioContext.
- */
-void aio_context_unref(AioContext *ctx);
-
-/* Take ownership of the AioContext. If the AioContext will be shared between
- * threads, and a thread does not want to be interrupted, it will have to
- * take ownership around calls to aio_poll(). Otherwise, aio_poll()
- * automatically takes care of calling aio_context_acquire and
- * aio_context_release.
- *
- * Access to timers and BHs from a thread that has not acquired AioContext
- * is possible. Access to callbacks for now must be done while the AioContext
- * is owned by the thread (FIXME).
- */
-void aio_context_acquire(AioContext *ctx);
-
-/* Relinquish ownership of the AioContext. */
-void aio_context_release(AioContext *ctx);
-
-/**
- * aio_bh_new: Allocate a new bottom half structure.
- *
- * Bottom halves are lightweight callbacks whose invocation is guaranteed
- * to be wait-free, thread-safe and signal-safe. The #QEMUBH structure
- * is opaque and must be allocated prior to its use.
- */
-QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque);
-
-/**
- * aio_notify: Force processing of pending events.
- *
- * Similar to signaling a condition variable, aio_notify forces
- * aio_wait to exit, so that the next call will re-examine pending events.
- * The caller of aio_notify will usually call aio_wait again very soon,
- * or go through another iteration of the GLib main loop. Hence, aio_notify
- * also has the side effect of recalculating the sets of file descriptors
- * that the main loop waits for.
- *
- * Calling aio_notify is rarely necessary, because for example scheduling
- * a bottom half calls it already.
- */
-void aio_notify(AioContext *ctx);
-
-/**
- * aio_notify_accept: Acknowledge receiving an aio_notify.
- *
- * aio_notify() uses an EventNotifier in order to wake up a sleeping
- * aio_poll() or g_main_context_iteration(). Calls to aio_notify() are
- * usually rare, but the AioContext has to clear the EventNotifier on
- * every aio_poll() or g_main_context_iteration() in order to avoid
- * busy waiting. This event_notifier_test_and_clear() cannot be done
- * using the usual aio_context_set_event_notifier(), because it must
- * be done before processing all events (file descriptors, bottom halves,
- * timers).
- *
- * aio_notify_accept() is an optimized event_notifier_test_and_clear()
- * that is specific to an AioContext's notifier; it is used internally
- * to clear the EventNotifier only if aio_notify() had been called.
- */
-void aio_notify_accept(AioContext *ctx);
-
-/**
- * aio_bh_call: Executes callback function of the specified BH.
- */
-void aio_bh_call(QEMUBH *bh);
-
-/**
- * aio_bh_poll: Poll bottom halves for an AioContext.
- *
- * These are internal functions used by the QEMU main loop.
- * And notice that multiple occurrences of aio_bh_poll cannot
- * be called concurrently
- */
-int aio_bh_poll(AioContext *ctx);
-
-/**
- * qemu_bh_schedule: Schedule a bottom half.
- *
- * Scheduling a bottom half interrupts the main loop and causes the
- * execution of the callback that was passed to qemu_bh_new.
- *
- * Bottom halves that are scheduled from a bottom half handler are instantly
- * invoked. This can create an infinite loop if a bottom half handler
- * schedules itself.
- *
- * @bh: The bottom half to be scheduled.
- */
-void qemu_bh_schedule(QEMUBH *bh);
-
-/**
- * qemu_bh_cancel: Cancel execution of a bottom half.
- *
- * Canceling execution of a bottom half undoes the effect of calls to
- * qemu_bh_schedule without freeing its resources yet. While cancellation
- * itself is also wait-free and thread-safe, it can of course race with the
- * loop that executes bottom halves unless you are holding the iothread
- * mutex. This makes it mostly useless if you are not holding the mutex.
- *
- * @bh: The bottom half to be canceled.
- */
-void qemu_bh_cancel(QEMUBH *bh);
-
-/**
- *qemu_bh_delete: Cancel execution of a bottom half and free its resources.
- *
- * Deleting a bottom half frees the memory that was allocated for it by
- * qemu_bh_new. It also implies canceling the bottom half if it was
- * scheduled.
- * This func is async. The bottom half will do the delete action at the finial
- * end.
- *
- * @bh: The bottom half to be deleted.
- */
-void qemu_bh_delete(QEMUBH *bh);
-
-/* Return whether there are any pending callbacks from the GSource
- * attached to the AioContext, before g_poll is invoked.
- *
- * This is used internally in the implementation of the GSource.
- */
-bool aio_prepare(AioContext *ctx);
-
-/* Return whether there are any pending callbacks from the GSource
- * attached to the AioContext, after g_poll is invoked.
- *
- * This is used internally in the implementation of the GSource.
- */
-bool aio_pending(AioContext *ctx);
-
-/* Dispatch any pending callbacks from the GSource attached to the AioContext.
- *
- * This is used internally in the implementation of the GSource.
- */
-bool aio_dispatch(AioContext *ctx);
-
-/* Progress in completing AIO work to occur. This can issue new pending
- * aio as a result of executing I/O completion or bh callbacks.
- *
- * Return whether any progress was made by executing AIO or bottom half
- * handlers. If @blocking == true, this should always be true except
- * if someone called aio_notify.
- *
- * If there are no pending bottom halves, but there are pending AIO
- * operations, it may not be possible to make any progress without
- * blocking. If @blocking is true, this function will wait until one
- * or more AIO events have completed, to ensure something has moved
- * before returning.
- */
-bool aio_poll(AioContext *ctx, bool blocking);
-
-/* Register a file descriptor and associated callbacks. Behaves very similarly
- * to qemu_set_fd_handler. Unlike qemu_set_fd_handler, these callbacks will
- * be invoked when using aio_poll().
- *
- * Code that invokes AIO completion functions should rely on this function
- * instead of qemu_set_fd_handler[2].
- */
-void aio_set_fd_handler(AioContext *ctx,
- int fd,
- bool is_external,
- IOHandler *io_read,
- IOHandler *io_write,
- void *opaque);
-
-/* Register an event notifier and associated callbacks. Behaves very similarly
- * to event_notifier_set_handler. Unlike event_notifier_set_handler, these callbacks
- * will be invoked when using aio_poll().
- *
- * Code that invokes AIO completion functions should rely on this function
- * instead of event_notifier_set_handler.
- */
-void aio_set_event_notifier(AioContext *ctx,
- EventNotifier *notifier,
- bool is_external,
- EventNotifierHandler *io_read);
-
-/* Return a GSource that lets the main loop poll the file descriptors attached
- * to this AioContext.
- */
-GSource *aio_get_g_source(AioContext *ctx);
-
-/* Return the ThreadPool bound to this AioContext */
-struct ThreadPool *aio_get_thread_pool(AioContext *ctx);
-
-/**
- * aio_timer_new:
- * @ctx: the aio context
- * @type: the clock type
- * @scale: the scale
- * @cb: the callback to call on timer expiry
- * @opaque: the opaque pointer to pass to the callback
- *
- * Allocate a new timer attached to the context @ctx.
- * The function is responsible for memory allocation.
- *
- * The preferred interface is aio_timer_init. Use that
- * unless you really need dynamic memory allocation.
- *
- * Returns: a pointer to the new timer
- */
-static inline QEMUTimer *aio_timer_new(AioContext *ctx, QEMUClockType type,
- int scale,
- QEMUTimerCB *cb, void *opaque)
-{
- return timer_new_tl(ctx->tlg.tl[type], scale, cb, opaque);
-}
-
-/**
- * aio_timer_init:
- * @ctx: the aio context
- * @ts: the timer
- * @type: the clock type
- * @scale: the scale
- * @cb: the callback to call on timer expiry
- * @opaque: the opaque pointer to pass to the callback
- *
- * Initialise a new timer attached to the context @ctx.
- * The caller is responsible for memory allocation.
- */
-static inline void aio_timer_init(AioContext *ctx,
- QEMUTimer *ts, QEMUClockType type,
- int scale,
- QEMUTimerCB *cb, void *opaque)
-{
- timer_init_tl(ts, ctx->tlg.tl[type], scale, cb, opaque);
-}
-
-/**
- * aio_compute_timeout:
- * @ctx: the aio context
- *
- * Compute the timeout that a blocking aio_poll should use.
- */
-int64_t aio_compute_timeout(AioContext *ctx);
-
-/**
- * aio_disable_external:
- * @ctx: the aio context
- *
- * Disable the further processing of external clients.
- */
-static inline void aio_disable_external(AioContext *ctx)
-{
- atomic_inc(&ctx->external_disable_cnt);
-}
-
-/**
- * aio_enable_external:
- * @ctx: the aio context
- *
- * Enable the processing of external clients.
- */
-static inline void aio_enable_external(AioContext *ctx)
-{
- assert(ctx->external_disable_cnt > 0);
- atomic_dec(&ctx->external_disable_cnt);
-}
-
-/**
- * aio_external_disabled:
- * @ctx: the aio context
- *
- * Return true if the external clients are disabled.
- */
-static inline bool aio_external_disabled(AioContext *ctx)
-{
- return atomic_read(&ctx->external_disable_cnt);
-}
-
-/**
- * aio_node_check:
- * @ctx: the aio context
- * @is_external: Whether or not the checked node is an external event source.
- *
- * Check if the node's is_external flag is okay to be polled by the ctx at this
- * moment. True means green light.
- */
-static inline bool aio_node_check(AioContext *ctx, bool is_external)
-{
- return !is_external || !atomic_read(&ctx->external_disable_cnt);
-}
-
-/**
- * aio_context_setup:
- * @ctx: the aio context
- *
- * Initialize the aio context.
- */
-void aio_context_setup(AioContext *ctx, Error **errp);
-
-#endif